package demo1;

// 实现双向链表 课程代码
public class MyLinkedList {
    static class ListNode {
        public int val;
        public ListNode prev;
        public ListNode next;

        public ListNode(int val) {
            this.val = val;
        }
    }

    public ListNode head;
    public ListNode last;

    public void display(){
        ListNode cur = head;
        while (cur != null) {
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
        System.out.println();
    }

    //头插法
    public void addFirst(int data){
        ListNode node = new ListNode(data);
        if (this.head == null) {
            head = node;
            last = node;
        }else {
            node.next = head;
            head.prev = node;
            head = node;
        }
    }

    //尾插法
    public void addLast(int data){
        ListNode node = new ListNode(data);
        if (head == null) {
            head = node;
            last = node;
        }else {
            last.next = node;
            node.prev = last;
            last = node;
        }
    }

    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data){
        if (index < 0 || index > size()) {
            System.out.println("index不合法");
            return;
        }

        if (index == 0) {
            addFirst(data);
            return;
        }
        if (index == size()) {
            addLast(data);
            return;
        }

        ListNode node = new ListNode(data);
        ListNode cur = searchIndex(index);

        cur.prev.next = node;
        node.prev = cur.prev;

        node.next = cur;
        cur.prev = node;
    }

    public ListNode searchIndex(int index) {
        ListNode cur = head;
        while (index != 0) {
            cur = cur.next;
            index--;
        }
        return cur;
    }

    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
        ListNode cur = head;
        while (cur != null) {
            if(cur.val == key) {
                return true;
            }
            cur = cur.next;
        }

        return false;
    }

    //删除第一次出现关键字为key的节点
    public void remove(int key){
        ListNode cur = head;
        while (cur != null) {
            if (cur.val == key) {
                if (cur == head) {
                    head = head.next;
                    if (head != null) {
                        head.prev = null;
                    }
                    break;
                }else if(cur == last){
                    last = last.prev;
                    last.next = null;
                    break;
                }else {
                    cur.prev.next = cur.next;
                    cur.next.prev = cur.prev;
                    break;
                }
            }else {
                cur = cur.next;
            }
        }
    }

    //删除所有值为key的节点
    public void removeAllKey(int key){
        ListNode cur = head;
        while (cur != null) {
            if (cur.val == key) {
                if (cur == head) {
                    head = head.next;
                    if (head != null) {
                        head.prev = null;
                    }
                }else if(cur == last){
                    last = last.prev;
                    last.next = null;
                }else {
                    cur.prev.next = cur.next;
                    cur.next.prev = cur.prev;
                }
                cur = cur.next;
            }else {
                cur = cur.next;
            }
        }

//        ListNode cur = head;
//        while (cur != null) {
//            if (cur.val == key) {
//                ListNode prev = cur.prev;
//                ListNode next = cur.next;
//                if (prev == null) {
//                    cur.next = null;
//                    if (next != null) {
//                        next.prev = null;
//                    }
//                    cur = next;
//                    head = cur;
//                }else if(next == null){
//                    cur.prev = null;
//                    prev.next = null;
//                    cur = prev;
//                    last = cur;
//                }else {
//                    prev.next = cur.next;
//                    next.prev = prev;
//                    cur.prev = null;
//                    cur.next = null;
//                }
//                //cur = cur.next;
//            }else {
//                cur = cur.next;
//            }
//        }
    }

    //得到链表的长度
    public int size(){
        int size = 0;
        ListNode cur = head;
        while (cur != null) {
            size++;
            cur = cur.next;
        }
        return size;
    }

    public void clear(){
        ListNode cur = head;
        while (cur != null) {
            ListNode curNext = cur.next;
            cur.prev = null;
            cur.next = null;
            cur = curNext;
        }
        head = null;
        last = null;
    }
}
